The present disclosure relates generally to digital editing of color images and more specifically to preserving color representations during color transformation processes.
Color images captured, generated, or represented by one device can be processed using a different device. This occurs, for example, when color images captured on film are digitized, digitally edited, and then transferred back to film. Because each device has its own color characteristics, a mathematical color transformation is needed to map colors from the source device color space to the destination device color space. To map colors from the destination device color space back to the source device color space, the mathematical transformation is inverted. Each color transformation must account for the color characteristics of both the source device and the destination device, therefore a unique color transformation is required for each source device-destination device pair. For example, editing color images captured on film of type X with a digital editing tool of type Z requires an X-Z color transformation from the film color space to the digital editing tool color space, while editing color images captured on film of type Y with a digital editing tool of type Z requires a Y-Z color transformation from the film color space to the digital editing tool color space. To accommodate all possible device pairings in a system of n devices, (n2−n)/2 unique transformations are required.
Device-independent color transformations map colors between a device color space and a standard color space S. For example, editing color images captured on film of type X with a digital editing tool of type Z can be accomplished using an X-S color transformation from the film color space to the standard color space, followed by an inverted Z-S color transformation from the standard color space to the digital editing tool color space. Editing color images captured on film of type Y with a digital editing tool of type Z can be accomplished using a Y-S color transformation from the film color space to the standard color space, followed by the same inverted Z-S color transformation from the standard color space to the digital editing tool color space. To accommodate all possible device pairings in a system of n devices, only n unique transformations are required: one between each device color space and the standard color space.